JCrawler is a free and open source extension, which means you can get it for free and you can do any modifications that you need. For a complete list of all the rights that you have or haven't, browse this site for the GPL license.
If JCrawler helps you gain some time or some money, and you feel you would like to thank us, there are some suggested ways:
say "Thank you" on the forum. People often underestimate the good feeling that a developer gets when someone appreciates his/her work.
say "Thank you" and rate our extension on the JED. Good advertising is always welcome.
donate something. This button will take you to PayPal to donate us the outrageous sum of € 5.00:
Money earned with donation will never be enough to pay even for a tiny part of our work... but still, it would be nice to have a beer paid by some happy JCrawler user :-)
And for those amongst you who still want to do more, answering or just sharing your experience on the forum is not a bad idea.