[laurent123456]

The article explains why it's important to trademark, but not how or more importantly if it makes sense for the majority of open source projects. If you need to hire a lawyer over several months to get a trademark, it's probably only possible for companies that also publish open source software.

[verdverm]

It can actually be rather cheap (as far as lawyers go). Mine cost about $2k per TM which includes USPTO fees.

It will depend on prior art, how close you are to others, how large the search needs to be, how many classes you are applying for.

[samtuke]

Just by starting to use the TM symbol next to words or images you intend to trademark is enough to offer some immediate and free protection (IANL)