> Is there a problem with someone owning it

Yes

> what?

They can decide you can't use it anymore

They can decide to charge more for it

They can arbitrarily take features out from under you or change how it works

They can read and/or sell/give away/accidentally get exploited and lose your data

They can prevent your extracting your data to move away from them

They can prevent you building or integrating other tools

They control how you can modify or configure the software

...