One example is Open-Xchange [https://www.open-xchange.com https://www.open-xchange.com] They make an open source webmail + drive + docs suite, and sell a comme

One example is Open-Xchange [https://www.open-xchange.com https://www.open-xchange.com] They make an open source webmail + drive + docs suite, and sell a commercial version (e.g. to ISPs). The software is great and they're still around, so it must be working out for them.