[kgwxd]

If the software is open then anyone can fork it, make it easier, more flexible, better in any way. So your support fee better be low enough that no one is motivated to do that instead of paying for support, and also hope no one ever does it just because they can and dont care about money.

[mcguire]

Could you name some products where this had happened?

[UncleMeat]

BCH. Led to a meaningful drop in the price of BTC after the fork.

[seba_dos1]

I don't think you can compare forking a blockchain with forking a free software project. Blockchain is just data and there are various wallets already available, so it didn't matter that the FLOSS code of the original wallet has been forked as much as the blockchain fork did.

[kgwxd]

JDK maybe?