Efer.io ( connected to Soc.io ) App Licensing?

Hi,

I had Efer.iohttp://www.eferio.com/ ) contact me about licensing a game I put out last year. They’ve offered me a one time fee for unlimited/lifetime downloads, which I honestly have no problem with, money. The sticking point is " Developer will provide functionality fixes in the case the APP proves to malfunction" this line makes me feel like their locking me into future app updates.

If anybody else did anything like this I’d love some feedback, thankyou.

Steve