Learn in the textbookSoftware Distribution and Usage Models
DefinitionFreeware (フリーソフトウェア) is software you can use without paying.
ExplanationEven when it costs nothing, the copyright stays with the author, so whether you may modify or redistribute it depends on the terms of use the author sets. The source code is not necessarily published.
AnalogyIt is like an exhibition at a museum with free admission. Looking costs nothing, but the rights to the works belong to the artists, and you cannot copy them and hand them out on your own.
Memory hookThe English word free means both "no charge" and "freedom". Here it is the no-charge sense.