Paint Net is free to download, install and use. It is more powerful than Microsoft Paint, and less complex that Photoshopping software, and there is no need to buy a subscription.
There is no official portable version of this program, but LiberKey have created a portable version of it that allows you to take the program around with you on a Flash drive. The portable version is also free and easy-to-use.
Microsoft has already replaced Microsoft Paint with a different program. If you prefer, you may download the old version of Paint, you may download and use Paint Net, and you may use the most modern Microsoft Paint replacement too. There is no rule that says you cannot have and use all three.
The software is free for personal users to use, and the terms and conditions do state that you may only use it for personal use. If you want a business or commercial licence, then you have to contact the company and pay for one.
You can set up the pictures for a GIF animation, but you will need another program to put it all together professionally. Paint Net is good for creating the animation GIF images, but you should use another piece of software for the actual animation side of it.
The software checks for updates every ten days, which means it has to contact the appropriate websites. You can turn off the automatic update feature. If your malware/virus checker asks you if you should block the signal, then it is up to you if you do. Maybe you would prefer to check for updates manually yourself.
Yes, this software has been designed so that it will work with multi-core devices, which means this program will work faster on more modern computers.
You can look and save .ico files, but Paint Net is a terrible icon-editing program. There are better icon editors out there, but if you are really stuck, you can always download and install an ICO plugin for this software.
The name and the general functionality are the only similarities with Microsoft Paint. Paint Net was built from the ground up by a different development team.
You cannot set JPG to be the default setting because whenever you save as a JPG, you lose a little bit of your image quality. In order to maintain the quality of your images, this software will use a PNG format if you are saving single layer images. A PDN format is used if you are trying to save multiple layer projects.