You buy a JUDLEX licence without leaving the application: you type your card details on the screen in front of you. That screen shows the button to pay once it has somewhere for you to type the card number, and not before. If you cannot pay there at that moment, the screen says so and points you to Support, which also sits one button away on the tariff screen, where you see what the licence costs.
You pay without leaving JUDLEX
The card form sits inside the application, so you type the number, pay and stay where you were. Your card details do not pass through JUDLEX servers.
Support, one button away
There are things about a payment that you cannot put right from your own computer. When payment is unavailable at that moment, the screen tells you so and gives you the route: Support. The tariff screen, where you see what the licence costs, carries that same button for questions about it.