Answering those two questions depends a bit on the "you" in the question. If "you" refers to the open source project/code, then both can be answered with a resounding "yes". If on the other hand "you" refers to you individually or as a company, then the first can be answered with a resounding "no" and the second a solid "maybe, that depends on how much you are willing to pay us for a 5 year support contract" (though you should probably word it a bit differently when talking with potential clients).

As far as working with source available components, suggestion one is to look for others int he community that you can cooperate with to maintain a fork, and option two, if you really can't get the community to support a fork, is to make it a plugin/optional component, preferably with an API so that other solutions can be integrated as options, or at least a fallback to the old version that was open source.