On some project mailing lists, you are allowed to post jobs like this. Some project sponsors even support this behavior with a dedicated job board website. But

On some project mailing lists, you are allowed to post jobs like this. Some project sponsors even support this behavior with a dedicated job board website. But: each project has different policies, and may even not have a policy if it's that new and no one has asked your question before. So write a polite email to the list asking if it is OK to post a help wanted job ad, and if yes, what are the guidelines. Do NOT include your job ad in this question email. If you get the all clear, fire away.