This response is based on the information provided.  We suggest you discuss with your contracting and finance team, program manager and/or legal department as appropriate.

While framed as a contracting question, this is a financial question regarding the use of fund types.

We believe, given the data provided and FMR 7000.14-R guidance, procurement funds (3080 for USAF) would be warranted; however, you need to review the budget documents as the request for the funding of those licenses and maintenance should have been in the budget documents and based on that evaluation you would use those funds for the purchase.  As noted above there is a $250,000 threshold in which one can use O&M funds for purchases.  We advise you should check with your Comptroller for the final decision on the use of the correct funds as the certifying funds officer (the Comptroller) will have to ensure the correct funds are used for this purchase.

Based on the question of using O&M funds versus Procurement funds, the Financial Management Regulation (FMR) 7000.14-R defines specific criteria and guidance.   The Federal Management Regulation Volume 2A Chapter 1 which explains the criteria for determining expenses versus investment costs which will direct you toward the use of Procurement funds or O&M funds. 

"FMR 7000.14-R 010201. Criteria for Determining Expense and Investment Costs

                A. Appropriation accounts form the structure for the President’s budget request and are the basis for congressional action. The appropriations are further organized into budget activities of appropriations with   programs, projects or activities of similar purposes. To support management of the Department of Defense’s programs, projects or activities, resource requirements should be organized and categorized   consistently within the appropriation and budget activity structure. The following sections provide guidance for categorizing resource requirements into the various appropriations.

                B. Basic Distinctions Between Expense and Investment Costs. The criteria for cost definitions consider the intrinsic or innate qualities of the item such as durability in the case of an investment cost or consumability in   the case of an operating cost and the conditional circumstances under which an item is used or the way it is managed. In all cases where the definitions appear to conflict, the conditional circumstances will   prevail. The following guidance is provided to determine whether a cost is either an expense or an investment. All costs are classified as either an expense or an investment. 

                                1. Expenses are the costs incurred to operate and maintain the organization, such as personal services, supplies, and utilities. 

                                2. Investments are the costs that result in the acquisition of, or an addition to, end items. These costs benefit future periods and generally are of a long-term character such as real property and   personal property.

                C. Policy for Expense and Investment Costs 

                                1. DoD policy requires cost definition criteria that can be used in determining the content of the programs and activities that comprise the Defense budget. The primary reasons for these distinctions are to allow for more informed resource allocation decisions and to establish criteria for determining which costs are appropriate to the various defense appropriations. 

                                2. The cost definition criteria contained in this policy are only applicable to the determination of the appropriation to be used for budgeting and execution. Cost definitions for accounting purposes are contained in Volume 1. 

                                3. Costs budgeted in the Operation and Maintenance (O&M) and Military Personnel appropriations are considered expenses. Costs budgeted in the Procurement and Military Construction appropriations are considered investments. Costs budgeted in the Research, Development, Test and Evaluation (RDT&E), Base Realignment and Closure (BRAC), and Family Housing appropriations include both expenses and investments. Definitions for costs within the Defense Working Capital Funds are provided in Chapter 9 and in Section 010214. 

                                4. Items procured from the Defense Working Capital Funds will be treated as expenses in all cases except when intended for use in weapon system outfitting, government furnished material (GFM) on new procurement contracts, or for installation as part of a weapon system modification, major reactivation, or major service life extension.

                D. Procedures for Determining Expenses Versus Investments. The following criteria will be used to distinguish those types of costs to be classified as expenses from those to be classified as investments for budgeting purposes: 

                                1. Expenses. Expenses are costs of resources consumed in operating and maintaining the Department of Defense. When costs generally considered as expenses are included in the production or   construction of an investment item, they shall be classified as investment costs. Military personnel costs are an exception to this rule. The following guidelines shall be used to determine expense costs: 

                                                a. Labor of civilian, military, or contractor personnel. 

                                                b. Rental charges for equipment and facilities. 

                                                c. Food, clothing, and fuel.  

                                                d. Supplies and materials designated for supply management of the Defense Working Capital Funds. 

                                                e. Maintenance, repair, overhaul, rework of equipment. 

                                                f. Assemblies, spares and repair parts, and other items of equipment that are not designated for centralized item management and asset control and which have a system unit cost less than the currently approved dollar threshold of $250,000 for expense and investment determinations. This criterion is applied on the basis of the unit cost of a complete system rather than on individual items of equipment or components that, when aggregated, become a system. The concept of a system must be considered in evaluating the procurement of an individual end item. A system is comprised of a number of components that are part of and function within the context of a whole to satisfy a documented requirement. In this case, system unit cost applies to the aggregate cost of all components being acquired as a new system. 

                                                g. Cost of incidental material and items that are not known until the end item is being modified are conditional requirements and are considered expenses because the material is needed to sustain or repair the end item. 

                                                h. Engineering efforts to determine what a modification will ultimately be or to determine how to satisfy a deficiency are expenses. 

                                                I. Facilities sustainment, O&M-funded restoration and modernization projects. Planning and design costs are excluded from the cost determination for purposes of determining compliance with the amounts established in 10 U.S.C. 2805 for minor construction projects; however, design costs are not excluded from capitalization. 

                                2. Investments. Investments are costs to acquire capital assets such as real property and equipment. The following criteria shall be used to determine those costs to be classified as investments: 

                                                a. All items of equipment, including assemblies, ammunition and explosives, modification kits (the components of which are known at the outset of the modification), spares and repair parts not managed by the Defense Working Capital Funds, that are subject to centralized item management and asset control. 

                                                b. All equipment items that are not subject to centralized item management and asset control and have a system unit cost equal to or greater than the currently approved expense and investment dollar threshold of $250,000 (for working capital funds investment criteria see Volume 2B Chapter 9 section 090103C). The validated requirement may not be fragmented or acquired in a piecemeal fashion in order to circumvent the expense and investment criteria policy. 

                                                c. Construction, including the cost of land and rights therein (other than leasehold). Construction includes real property equipment installed and made an integral part of such facilities, related site preparation, and other land improvements. (See paragraph F below for special guidance concerning real property facilities.) 

                                                d. The costs of modification kits, assemblies, equipment, and material for modernization programs, ship conversions, major reactivations, major remanufacture programs, major service life extension programs, and the labor associated with incorporating these efforts into or as part of the end item are considered investments. All items included in the modification kit are considered investment even though some of the individual items may otherwise be considered as an expense. Components that were not part of the modification content at the outset and which are subsequently needed for repair are expenses. The cost of labor for the installation of modification kits and assemblies is an investment. 

                                                e. Supply management items of the Defense Working Capital Funds designated for weapon system outfitting, government-furnished material on new procurement contracts, or for installation as part of a weapon system modification or modernization, major reactivation or major service life extension. 

                                                f. Also considered as investments are support elements such as data, factory training, support equipment and interim contractor support (ICS), which are required to support the procurement of a new weapon system or modification."

If you and your comptroller agree this is a new "within scope" requirement and it is greater than $250,000 it is not optional to use procurement vs. O&M funds, it is required.  But the $250,000 referred to in the FMR and AFI 65-601 is for a system unit cost.

We do not know the details of the acquisition or the ensuing contract, but in the background provided you stated the contract was recently awarded (four months ago) which, again based on the data provided, we are taking to mean the exercise of the option.  We are not clear on the original scope, but if the original was for all USAF desktops increasing numbers and acquiring new licenses could fall under the original scope.  You will want to create a new contract line item number (CLIN) for the new requirement funded with procurement dollars.