Honestly, we can't vouch for them since we are not very familiar with this supplier, having had no personal experience in dealing with them.
But I did check their site and they seem pretty legit. Although they are quite new and have been online for roughly 6-7 months only (we usually recommend dealing with suppliers who have been online for at least 2years - for safety and security reasons).
Also make sure that your PayPal is linked to your credit card and not your bank account. Note that PayPal will not strongly pursue chargebacks/disputes for purchases outside eBay. Whereas if your PayPal is linked to your credit card, should anything go wrong you can always call your credit card company and do the chargeback from that end.
You may also want to ask them for documents to prove that the software they are selling are authentic and not just copies. Try to get to know them better before paying for anything.
Hope this helps.