You can download the trial version from Aseprite website: https://www.aseprite.org/trial/
In the trial version you cannot save images, and the only way you'll find to move your unsaved work from the trial version to the official version is using copy-and-paste of each canvas/cel.
This kind of trial version is really good, because people are able to fully try out program before buying it. Like other programs limit tools and add a huge watermark over everything.#Awesome
can i use trial version for commercial work?
Do you mean taking screenshots or copying-and-pasting your artwork? Yes, you can! Remember that you will not be able to save the whole animation/layers/etc. (e.g. in a .ase or .gif file) with the demo version.