Can I tag my site images for Google's "Label for reuse" and such? I appreciate any feedback.
P.S. Does Meta keywords do anything anymore?
This method of tagging images for licensing is the correct method of doing so. In most cases you are already wrapping your images in some type of block element as it is for styling etc, so adding the about attribute along with a license copy link is just another few seconds of code.
What we be appreciated from a developers standpoint would be if you could have all of the images on your page (in a gallery for instance) tagged with the correct wrappers and a single license attribution link at the bottom of that page as a blanket for all of the images currently being viewed.
For your seconds question, keyword metas are a bit of a conundrum. OF the 3 major search engines (Google, Yahoo, and Bing) the following is a brief synopsis of their current stance on keyword metatags.
Google - does not use them Yahoo - rarely uses them when no other SEO ranking factors can be found on the page Bing - Uses them to very little extent that has a very low flagging factor in their ranking algorithm
Keyword stuffing in a meta tag can get your page devalued and marked as spam by Bing if it is found that the keywords trigger spam flags based on other page content
In the long run you are likely to do more harm than good by using them.
Hope that helps.