https://github.com/ElemeFE/el.
has License type on the far left, and this item is MIT

refer to https://baike.baidu.com/item/.

• the licensee has the right to use, copy, modify, merge, publish, distribute, sublicense and sell copies of the software and software.
• the licensee can modify the license terms to the appropriate content according to the needs of the program.
• copyright and license notices must be included in the software and all copies of the software.
• this license term is not a free software license of copyleft and is allowed to be used in free / open source software or non-free software (proprietary software).

there is an one-picture stream in Ruan Yifeng's blog. You can see
http://www.ruanyifeng.com/blo.

of course. You need to see other people's CSS, downloaded and directly referenced in CSS. You can refer to uiw-iconfont

this is an open source MIT, that can generate its own font file through svg images

@font-face {font-family: "w-iconfont";
  src: url('w-iconfont.eot?t=1530897617382'); /* IE9*/
  src: url('w-iconfont.eot?t=1530897617382-sharpiefix') format('embedded-opentype'), /* IE6-IE8 */
  url('w-iconfont.ttf?t=1530897617382') format('truetype'), /* chrome, firefox, opera, Safari, Android, iOS 4.2+*/
  url('w-iconfont.svg?t=1530897617382-sharpw-iconfont') format('svg'); /* iOS 4.1- */
}

[class^="w-icon-"], [class*=" w-icon-"] {
  font-family: 'w-iconfont' !important;
  font-size:16px;
  font-style:normal;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.w-icon-adobe:before { content: "\ea01";}
.w-icon-ali-pay:before { content: "\ea02";}
.w-icon-aliwangwang:before { content: "\ea03";}