作为一款免费的应用程序，使用它应该是没有任何阻碍和成本。
As a free application, there are no barriers or costs to trying it out.
迷信行为也不是免费的——种种仪式和避讳都有成本。
Superstitions are not free - there are rituals and avoidances cost.
“付你能付”的培训活动关注在保持低成本，通过选择免费或低价的场所，并要求参与者自带电脑和装备来控制成本。
Pay-What-You-Can training events focus on keeping costs low by taking place in free or low cost venues and asking participants to bring their own supplies and laptops.
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