If you're asking whether you'll be able to get a reference from the forum or the signature campaign managers I'd say; no, and probably not.
When it comes to a CV/Resume
formal work, and freelancing could be considered the same as LoyceV pointed out. I don't think I've come across an employer that specifically states
formal work experience. I'm not even sure I quite grasp what that means, since work is work whether you're directly employed or a contractor, i.e a freelancer. As long as it's relevant to the job you're applying for, and actually somewhat substantial then include it. However, would I put signature campaign advertisement on my resume? No.
Although, if you did you'd have to put something down like work experience of advertising, and tell them exactly how you did that. Honestly, it probably isn't going to add much to your CV, since it's a simple process which doesn't require much if any skill at all.
I'd much rather personally replace that with more important content. The employer could easily assume you're just trying to pad the resume up.
However, signature campaign earnings need to be declared to your tax man. Obviously, this is dependant on your countries rules, but generally it's considered income, and therefore needs to be declared, and taxed, which I think a lot of users are missing. So, just because it's not deemed substantial enough for your resume, doesn't mean you avoid paying tax on it. I know that's slightly unrelated to the question, but I thought it was important side note to include.
By being official, it means there are documents and contracts signed. There are full benefits and rights and everything like the normal employee we knew as prescribed by our laws. Even some informal workers have signed contracts too but no full benefits and they aren't long-term.
A lot of freelancers end up signing contracts. So, there's no real distinction due to a contract being present or not. Plus, any work in the eyes of the tax man will be deemed as income, regardless if contracts have been signed or not. So, ultimately it's work in the eyes of the tax man. I personally wouldn't consider it as work, since I'm just doing what I'd be doing if I wasn't get paid for it. So, it's just a benefit for me. Obviously still taxed as above.