I have written some open source (MIT License) software. I wrote the software for my own company Company A, that is legally registered with myself as the only employee. I only registered it so I could contract between jobs.
Recently I began a new full-time job in a senior position Company B, and we build software, as an agency, for some very large global companies Company X.
If I build software in Company B and use some of the open source libraries I built in Company A, can Company A say the open source software is used by Company X?
Essentially I want to create a public web page about the open source software, and I want to know if I can say it's used by Company X?
or something like: used in Company X's Product X?