InDesign CS4 for Mac

I'm looking to buy InDesign for my intel iMac after using the trial version
for the past 30 days and I can across several online software sellers offering InDesign for around $250 or $300. They say it's legit and new software but
only for installing in one computer, one time. ZTech is one seller.. Royal Discount is another. Is it legal to use this software? I have a hard time paying the full price to Adobe and this looks attractive, but I want to be legal.
Anyone out there buy from these guys? And are there any other alternatives?
Thanks in advance.

I'm not sure about the specific sellers you are talking about, but it's probable that they are legit. Do a little digging, check out the companies in general. Since CS4 is now a version outdated, I wouldn't be entirely surprised if there were some discounts now. Also, I assume you're not looking at an upgrade? (I know it's a stupid question, just covering the bases ).

Thanks..

I haven't found too much negative about those two I mentioned in my post other than less than satisfactory customer service now and then. The InDesign CS4 is a full version, not an upgrade. But you can only install it on one computer. Says nothing about not registering with Adobe. As a matter of fact, they say I can get upgrades from Adobe with no problem. Thanks for the reply.