Is buying a developer account or paying an annual subscription to upload applications and subscribe to a payment service that charges a 30% or 15% commission on profits considered usury (riba) or a prohibited transaction?

There is no objection to combining the contracts of ijarah (leasing/renting) and samsarah (brokerage). Ijarah here refers to uploading applications to the store for a fee, and samsarah is the store taking a percentage of the sales. The majority of scholars prohibit stipulating one contract within another, as it falls under "two transactions in one." However, Sheikh al-Islam Ibn Taymiyyah and many contemporary scholars have permitted it, as long as it is not a stratagem for riba (usury), arguing that the prohibition of "two transactions in one" relates to bay' al-'inah (a specific type of buy-back sale). Accordingly, there is no objection to uploading applications to the store for a fee while the store also takes a commission upon sale.