If I buy some advertising (Adwords or something) and then use htaccess or something similar to redirect the traffic to my referral link, is that against TOS? The traffic would be coming from my site, but they might not be happy with the way its coming. Ultimately, however, the person was not forced to click the link or view it in a popup, etc.
Not sure about CJ - they're usually happy as long as you're making sales/conversions. Why not just use the advertisers CJ urls in your PPC links? Redirecting might be against the Adwords TOS.
That's perfectly fine as long as you follow advertiser's PPC regulations (read their Keyword Link, program description, and any special terms). FYI, a htaccess redirect (Redirect or RedirectPermanent, or any other form) will not show your site as the referrer - it'll show Google. Same with a PHP location header redirect - it just does a HTTP 301/302 redirect (same way CJ redirects through their tracking links).
Meta refreshes should do that, however, CJ will probably start asking how you're sending traffic in that case. Why are you trying to mask the referrer?
Sorry if I wasn't clear above with my explanation - PHP header redirects act the same as .htaccess redirects, so it still won't show the referrer as your site.
Meta refreshes should show your site as the referrer if I remember correctly, but I can't be 100% sure without testing it first. Unless you're trying to mask the source of the traffic, I'd go with a PHP or htaccess redirect. If you are trying to mask the source (which you said you weren't), then that might cause some issues with CJ's Network Quality department.