"... bajo determinadas condiciones"

Se explica este tipo de convenio en este extracto:

On March 7, 2003, the Company announced that is had signed a letter of intent to enter into a comprehensive ***Off-Take*** Purchasing and Investment agreement with Lazare Kaplan International Inc. The agreement provides a
guarantee from Lazare Kaplan to purchase a minimum of 75% to a maximum of 100% of the output of the project,
with Tahera holding the right to limit this percentage to 75%. The agreement also provides Tahera the option to enter
into a rough-diamond marketing agreement and/or a polishing agreement with Lazare Kaplan. In addition, Lazare
Kaplan will receive warrants entitling it to purchase US$4 million of common shares in the Company at $0.22 per share.

(en el resto del mismo hay también referencias a "off-take arrangement" y "off-take agreement".)

Se trata básicamente de que una empresa minera logra vender su producción a un sólo comprador sin tener que ponerla en el mercado; y a cambio de esto, la minera concede ciertas ventajas al comprador.

"to take something off someone" de una manera general significa comprarlo en un gran volumen para que el vendedor no tenga que venderlo por partes a muchos compradores.

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Note added at 25 mins (2008-03-05 20:20:19 GMT)
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http://www.tahera.com/Theme/Tahera/files/FinancialReports/20...