If you are one of those who when downloading an application, is annoyed by so many ads, we must say that TubeMate Youtube Downloader is one of the applications that have less advertising. Also, the banners are not invasive at all or annoying so you do not have to worry. But to tell the truth, this application does not have the option to be used without advertising.
Everyone who is an application developer or programmer needs to generate income from their work and one of the best sources of income is advertising. Also, it requires a long investment in improvements and maintenance that is not done for free. Top applications like these have a balance between the amount of advertising and downloads that will likely generate quite a bit of revenue, both to maintain the application and to support themselves. Although only the developers of the app know how much money they generate.
How legal is it? With the vastness of the Internet, finding a loophole is easy, although it is true that there is hardly any difference between watching the videos when you want via streaming and watching them when you want without spending data. Another very different thing would be to download the video and manipulate it or publish it in your name, so the responsibility of the video is on who downloads it and not on who facilitates the download.
That is why Google does not accept this app in its store, however, the restrictions that Google places on applications when uploading them are increasing. Although we can always resort to alternative stores such as the Malavida website to download your APK.