Tools and costs

Licensing of Microsoft products has historically been a minefield of complexity. You can even sit for an official exam on it and get a qualification. Microsoft's recent move toward open source practices is very encouraging, as the biggest benefit of open source is not the free monetary cost but that you don't have to think about licensing costs. You can also fix issues, and with a permissive license (such as MIT), you don't have to worry about much. The time costs and cognitive load of working out licensing implications now and in future can dwarf the financial sums involved (especially for a small company or startup).