Absolutely. For the first startup that I worked for, I earned a position with budgeting authority. Once we achieved profitably, I added donations to the open source tools we relied upon. I received some pushback and defended it. Looking back, I am proud of that choice. I encourage you all to do the same.
One argument I made was sponsoring a project, especially buys you support / developer relations. For example, we replaced a commercial PKZIP license with 7-zip. Was able to use the fact that one of the project we donated to, 7-zip, implemented a feature request that helped in this transition. That combined with the fact that these donations relative to our proprietary software costs were insignificant, made it an easy sell to my boss.
What likely works better in conservative environments, are not donations, but (generous) support contracts. This is something buisness people can understand.
