I'm not sure much can be done. There are lots of competing chess chat sites. So when one is not very busy, like this one, people stop checking it out - hence less potential posters. And it is posters that keep the forum alive - there must be different topics of interest on a regular basis so people check it regularly to see if there is something new they want to comment on.
Here I think it is likely only going to be for the regular Chess5'ers who want to share an idea with one of the other regulars, to see if they can get any responses. Only the regulars probably check out this forum on some periodic basis. This may be the best that can be achieved.
The only other suggestion I have is for the admin to post something controversial, interesting, timely on some type of regular basis, so that there is something new regularly for them to consider posting on.
I have made it a point to do some posting here, especially on topics of Canadian interest, since there are a lot of Canadians who access the site. And I hope it will be of interest to players from other countries as well. But you need a number of dedicated posters, willing to post regularly, to keep a site alive. And this site doesn't have the required committed regular posters - hence my suggestion that maybe admin can fill the void until hopefully the site starts generating its own new regular posts.